1. Field of the Technical Disclosure
The present disclosure relates generally to sampling circuits, and more specifically to an improved correlated double sampling technique.
2. Related Art
Correlated double sampling (CDS) generally refers to a sampling technique in which the strength of a signal at a node is determined as a difference of a strength at the node when the signal is coupled to the node and a strength at the node when the signal is decoupled from (or in general, not provided to) the node. CDS is often employed when the node may contain unknown non-signal components which can be treated as an offset or low frequency noise, as is well known in the relevant arts.
As an example, correlated double sampling is often employed in imaging systems that use charge coupled devices (CCD) as the image sensors. Before the charge of each pixel is transferred to an input node of a charge-to-voltage converter receiving the charge output by the CCD, the output node is reset to a reference value. The reference value is then sampled (first sampling interval). The pixel charge is then transferred to the output node, and the output node is sampled again (second sampling interval). The first sample is subtracted from the second sample, with the difference (voltage or current) representing the charge collected by the pixel.
It is often desirable that CDS be implemented while meeting the various requirements of the specific environments in which CDS is employed.
In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the corresponding reference number.